1. Field of the Invention
The present invention relates to a polymer membrane for facilitated olefin transport and a method for fabricating the same. More particularly, the present invention relates to a polymer membrane for facilitated olefin transport, coated with positively charged silver nanoparticles, which shows excellent selectivity for olefins over paraffins and thus stably conducts the facilitated transport of olefins for a long period of time, and a method for the fabrication thereof.
2. Description of the Related Art
Polymer membranes have found applications in separation of various mixtures into individual constituents, particularly into carbon dioxide and methane, into oxygen and air, and into organic vapor and air. However, conventional polymer membranes are not sufficiently capable of separating olefins and paraffins, for example, propylene and propane, butylene and butane, and the like, because olefins and paraffins are similar in molecular weight and physical properties.
With the introduction of the concept of a facilitated transport as a solution to the problem of difficulty in separating olefins and paraffins having similar molecular weights, active research has been conducted to apply polymer membranes for separation therebetween.
Facilitated transport, also known as facilitated diffusion, is a process of diffusion, a form of passive transport, where molecules diffuse across membranes, with the assistance of transport molecules, called carriers, which are solute specific. In contrast to active transport, facilitated transport does not require energy, and carries molecules or ions down a concentration gradient. A polymer membrane for facilitated transport has thereon a carrier which can reversibly react with specific molecules of a mixture in order to separate them. Across a facilitated transport membrane, thus, a specific molecule (for example, an olefin molecule) not only diffuses due to a concentration gradient, based on Fick's law, but also is transported by the carrier specific thereto with an increase in selectivity and transmittance.
For facilitated transport, solid or liquid membranes on which a silver salt, for example, AgBF4 or AgCF3SO3, is supported as a carrier, have been suggested. An initial model of the Ag-bound membranes suffers from the disadvantage of a decrease in the activity of the silver salt bound thereto with an increasing usage time period. Phthalate compounds or surfactants have been suggested in order to prevent the silver salt from decreasing in activity.
However, silver salts in combination with conventional surfactants, such as phthalate compounds, need an additional humidifying process and cannot maintain selectivity for olefins over paraffins for a long period of time.
Therefore, there is a need for a novel transport system that not only exhibits high selectivity for olefins, but also maintains the facilitated transport performance at a high rate for a long period of time.
Exhibiting characteristic physicochemical properties in various fields, including surface-enhanced Raman-scattering, catalysis, photonics, and sensors, silver nanoparticles have lately attracted considerable attention. The characteristic physicochemical properties of silver nanoparticles, different from those of silver or silver salts, are attributed to the greater reactivity based on the larger surface area of nanoparticles.
For example, an experiment for the reaction of silver nanoparticles with oxygen molecules at low temperature demonstrated that smaller nanoparticles exhibit higher ability to decompose oxygen molecules into atoms. On the other hand, when reacted with bulk nanoparticles, oxygen molecules are for the most part decomposed into O2−5. Silver nanoclusters in an aqueous solution are known to have the ability to transport electrons to suitable acceptors and take partial positive charges if the circumstances permit, thereby showing superior chemical activity.